1. Field of the Invention
The present invention relates to injection devices, and in particular, it relates to an injection device that uses a conventional syringe in delivering one or more preselected doses of a drug.
2. Description of the Prior Art
Daily self-administered hypodermic injections are a common form of drug administration for many persons suffering from diseases such as diabetes. In the case of a diabetic, insulin is administered on a daily schedule which is designed to correspond to high levels of glucose within the cardio-vascular system. The schedule of administration of insulin varies among diabetics according to the needs of the diabetic and the type of insulin being used.
There are basically three types of insulin: short-acting, intermediate-acting, and long-acting insulin. The most commonly used insulins are Regular and Lente (short-acting insulins) and NPH (intermediate-acting insulin). Intermediate and long-acting insulins are administered once or twice a day. The short-acting insulins are normally administered at mealtimes to counter high levels of glucose associated with meals. Normally, the dosage of, for example, Lente insulin is a rather small dosage ranging from 0.3 to 0.4 c.c. before a meal.
However, the injection of insulin at every meal is quite an inconvenience, especially when dining out. It is crucial to many diabetics to take a dose of regular insulin at each mealtime. However, because of the inconvenience, most diabetics do not take the injection and maintain dangerously high glucose levels. For each injection, alcohol, a bottle of insulin and a syringe is needed. The area of the body where the injection is to be made needs to be cleansed with alcohol and then the syringe must be loaded with insulin from the bottle. When the injection is made, in the case of a disposable syringe, the syringe is thrown away after only one injection of a small amount of insulin. When a nondisposable syringe is used, the syringe needs to be cleaned prior to being used again. In either case, it is very inconvenient to prepare for the injection, administer the injection, and in the case of a nondisposable syringe, to clean the syringe afterwards.
There have been several attempts in the prior art to make the injection process more convenient and to ensure that the amount of the dosage for each injection is precise.
In the Yochem U.S. Pat. No. 2,739,591, a device which is attached to a syringe permits the user to administer successive uniform injections. The device is used in a situation where a technician or physician is administering the same uniform dosage to a number of people. However, the device does not permit a single user to conveniently self-administer insulin from one mealtime to the next. First, no provision is made for the needle to be kept sterile between injections. Second, considerable care must be taken in carrying a loaded syringe so that the syringe is not accidentally actuated.
The Kyrias U.S. Pat. No. 3,720,211 describes a device that manipulates a hypodermic syringe to automatically administer an injection. However, the device of the Kyrias Patent expells the entire charge within the syringe and is useful for only one injection.
The Stein U.S. Pat. No. 3,677,246 shows a hypodermic syringe having a relatively small injection chamber with an adjustable volume and with a second relatively larger supply chamber which is adapted to hold a relatively large supply of injection solution. The smaller injection chamber is connected to the larger supply chamber and a pump is associated with the supply chamber, operable by a plunger from outside the syringe, to supply injection solution to the injection chamber. This type of syringe has the disadvantage of being complex in construction and expensive to manufacture.
Other patents, the Gasaway U.S. Pat. No. 3,688,765, the Scherer et al U.S. Pat. No. 2,460,039, the Wallin U.S. Pat. No. 2,373,520 and the Sarnoff U.S. Pat. No. 3,712,301, describe other devices for use in injecting solutions. However, none of these devices are sufficiently practical and convenient for an insulin administration schedule.